Setting a Trap for Antimatter
Transcript of Setting a Trap for Antimatter
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Gabrielse
Setting a Trap for Antimatter
Gerald Gabrielse, ATRAP Spokesperson (CERN)Leverett Professor of Physics, Harvard
2006
Science and science fiction
Warning: This Talk is Not About Science Fiction.
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Gabrielse
Matter and Antimatter? Particle and Atoms of Matter and AntimatterAnnihilation ChallengesTraps: Containers Without WallsMaking Antimatter Atoms?Why Should We Do This?
Setting a Trap for Antimatter
Support fromNSF, AFOSR
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Gabrielse
Where Did You Learn About Antimatter?
Antimatter annihilation powered Star Trek space ship “Enterprise”“going boldly where no one had gone before”
Dr. Spock “knew”
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GabrielseGenerations of Trekies
We study antimatter. How close are we to the Star Trek imagination?
hardware: android software: hologram
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GabrielseThe Science Reality
Behind the Science Fiction Imagination
What is Matter?
What is Antimatter?
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GabrielseWe Are Made of Matter
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GabrielseParticles of Matter and Antimatter:
Opposite and Identicalcharge mass
Only measurements tell how identical
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Gabrielse
Matter and Antimatter Atoms
Particle and antiparticle charges are opposite
Both atoms are uncharged same charge
unchargedatom
unchargedanti-atom
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Gabrielse
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Gabrielse
According to Physics as We Understand ItLooks Like the Whole Universe
Could Have Been Made of Antimatter
How would an antimatter universe be different?
Why is our universe made of matter rather than antimatter?
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Gabrielse
What Would I Look LikeIf I Were Made of Antimatter?
• protons antiprotons• neutrons antineutrons• electrons anti-electrons (positrons)
?Less mass?
Handsome?
More intelligent?
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Gabrielse
Big disappointment:• Antimatter Gabrielse looks the same!• Antimatter Gabrielse has the same mass!• Antimatter Gabrielse has the same limited brain power!
AntimatterGabrielse
What Would I Look LikeIf I Were Made of Antimatter?
• protons antiprotons• neutron antineutrons• electrons anti-electrons (positrons)
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Gabrielse
Universe Made of Antimatter
• Essentially the same as a universe made of matter
• We only know two ways for inhabitants to know whether theylive in a universe made of matter or antimatter
(Need a large accelerator complex and sophisticated techniques)
Why is our universemade of matter?
(seems like antimatter would work just as well)
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Gabrielse
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Gabrielse
Why Are Science Fiction Writersso Fascinated?
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GabrielseAntimatter and Matter ParticlesAnnihilate Each Other
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Gabrielse
What Happens When
Anti-Gabrielse Gabrielse
Antimatter and Matter Gabrielse Meet?
About to shake hands
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GabrielseHuge Energy Release!
2E mc=
energyreleased
mass thatdisappears 200 kg
Einstein’s famous formula
100 kgAnti-Gabrielse
100 kgGabrielse
5,000,000,000,000 kilowatt-hoursYearly output of 500 nuclear power plantsEnergy from 4200 Megatons of TNT
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Gabrielse
Efficiency
Annihilation 100 %
Nuclear fission 0.1 %Nuclear fusion 0.1 % (or a bit higher)
Chemical fuel 0.000 000 3 %
Annihilation• 1000 times more bang for the gram
compared to nuclear fuel
Energy Released= Mass of Fuel Used
Energy Source of the Future? No, certainly notAntimatter Weapons? No, certainly notAntimatter Rockets? Doubtful, … maybe in
distant future
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GabrielseAntiproton Trapping and Annihilation Makes its Way Into Popular Culture
Serious Play: HapgoodAuthor: Tom Stoppard
Fiction best seller
Star Trek – antimatter powers the space ship Enterprise
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Gabrielse
Should the Pope Have Worried?
Missing detail: if all the antiprotons we have madein the history of the world were annihilatedat the same time
Not enough energy to boil a pot of tea
Clearly the pope should havestudied more science
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Gabrielse
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Gabrielse
Embarrassing, Unsolved Mystery:How did our Matter Universe
Survive Cooling After the Big Bang?
Big bang equal amounts of matter and antimattercreated during hot time
As universe cools antimatter and matter annihilate
Big Questions:
• How did any matter survive?
• How is it that we exist?
Our experiments are looking for evidence of any way that antiparticles and particles may differ
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Gabrielse
Our “Explanations” are Not so Satisfactory (My opinion)
Baryon-Antibaryon Asymmetry in Universe is Not UnderstoodStandard Explanation• CP violation• Violation of baryon number• Thermodynamic non-equilibrium
Alternate• CPT violation• Violation of baryon number• Thermo. equilib.Bertolami, Colladay, Kostelecky, PottingPhys. Lett. B 395, 178 (1997)
Why did a universe made of matter survive the big bang?Makes sense look for answers to such fundamental questions
in the few places that we can hope to do so very precisely.
Bigger problem: don’t understand dark energy within 120 orders of magnitude
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Gabrielse
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Gabrielse
Low Energy Studies of Antimatter
CERN Laboratory (Geneva) makes it
We slow it, catch it, cool it, study it
Need a container without walls to avoid annihilation
trap
Starthere
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Gabrielse
Particle Trap – A “Container Without Walls”
Horseshoe Magnet
- - -
- - -
negativeantiproton
Need two truths to understand particle trap1. Charged particles go in circles near a magnet2. Same sign charges repel
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Gabrielse
ATRAP – Trap and Detectors
fibers77 K
BGO77 K
antiprotons
positronsource
positron traps
antiproton traps
rotating electrode
5.3 Teslamagnetic
field
4.2 K
Harvard: Trap, vacuum, rf electronicsJuelich: Scintillation detectors Garching, York, Mainz: Lasers
Small View
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Gabrielse
(Harvard)
Approx.100 leads(Photo by P. Horowitz)
Penning Trap
Rotating• 4 K, 6 Tesla• electrode• single crystal• field emissionpoint
1 cm
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Gabrielse
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Gabrielse
One Charged Particle in a TrapOne electron more than 10 months One antiproton several months
Can study the particle properties with extremely high precision
Antiproton and proton have the same charge-to-mass ratioto better than 1 part in 1010 = 10000000000Measure the electron magnetic moment to better than 1 part in 1012 = 1000000000000
Gives a new value for the fine structure constant αthat is much more accurate
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Gabrielse
One-Antiproton Radio
Tuning
FM Radio
Speaker
Antenna
frequency tuning
“volume”
So far, the most stringent CPT test with baryons comes from
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GabrielseSpecial Relativity Is Crucial year of EinsteinPlan: Compare cyclotron frequency for antiproton and proton
compares Q/M for antiproton and proton (if B stays same)test of CPT invariance for baryon/antibaryon system
Problem: Antiproton cyclotron frequency shifts in time
cQ BM
ω =
cQ BM
ωγ
=
21
111
1.000000001
KMceVGeV
γ = +
= +
=
Highly non-relativistic antiproton
Actually, highly “relativistic” at 1 eV due to high resolution
Extrapolate Einstein awayK 0 eV
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Gabrielse
Polarization Effect Discovered with Molecular IonsJ.K. Thompson, S. Rainville and D.E. Pritchard, Nature Lett. 430, 58 (2004)
Motional radial electric field: E = vBpolarizes the ion radially: d = αE = -αvB
Ion experiences • magnetic force on its charge: -evB• additional force on it dipole moment: -dωΒ
The additional polarization force could be expected to vanishas we take the v 0 limit in our experiment
But, it does not. Instead2
70 pptc
c
BM
ω αω∆
= − =
not really statistically significant(an excuse to measure more accurately?)
corrected
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Gabrielse
year
1960 1970 1980 1990 2000
fracti
onal
accu
racy
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
CERNBNL
ppb
0
1
2
TRAP I
(a) (b)Bevatron (p discovery)
TRAP II
Trap II
TRAP III
TRAP III
(exoticatoms)
TRAP Improved the Comparison of Antiproton and Proton by ~106
G. Gabrielse, A. Khabbaz, D.S. Hall, C. Heimann, H. Kalinowsky, W. Jhe;Phys. Rev. Lett. 82, 3198 (1999).
100antiprotonsand protons
/ (antiproton) 0.99999999991(9)/ (proton)
q mq m
= −119 10 90ppt−× =
56 10×
best CPT test with baryons
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Gabrielse
Last TRAP Measurement of Antiproton Q/M
improvedapparatus
and technique
Low Energy Antiproton Ring(LEAR) shut down
Could do significantly better!
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Gabrielse
could q and m change to keep q/m constant?
TRAP: Directly compare q/m for antiproton and protonASACUSA: Indirect measure of q2m for antiproton
- antiprotonic He spectroscopy - and detailed structure calculations- measured Rydberg constant, etc.
Comparisons of Antiproton and ProtonTRAP: q/m same to fractional accuracy 0.000 000 000 09
ASACUSA: q2m same to fractional accuracy 0.000 000 06Together: q and m same to fractional accuracy 0.000 000 06
q/m comparison is 700 times more accurate
Q/M much more accurate than Q and M separately
Given that q/m magnitudes are the same,
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Gabrielse
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GabrielseDigression: Quantum Limit
of a Particle in a Trap
0.1 µm
2ψ
Student award symposium: Brian Odom, Thursday, 2 pm
One ElectronQuantum Cyclotron
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GabrielseQuantum Cyclotron
1 5 0 G H zcυ ≈
Tesla6B ≈
one electron quantum
average quantum number < 1, etc. quantum
n = 0n = 1n = 2n = 3n = 4
7.2 kelvincω =
To realize a quantum cyclotron: • need cyclotron temperature << 7.2 kelvin• need sensitivity to detect a one quantum excitation
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Gabrielse
Cylindrical Penning Trap
Electrostatic quadrupole potential good enough near trap center
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Gabrielse
Quantum Jumps as a Function of Temperature• one electron• Fock states of a cyclotron oscillators• due to blackbody photons
0.23
0.11
0.03
9 x 10-39
On a short time scalein one Fock state or another
Averaged over hoursin a thermal state
average numberof blackbody
photons in the cavity
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Gabrielse
Quantum Jump Spectroscopy
• lowest cyclotron and spin states• one electron in a Penning trap
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GabrielseA New Measurement
of the Electron Magnetic Moment
BSgµ µ=magnetic
momentspin
Bohr magneton2em
• First improved measurement since 1987• Nearly six times improved accuracy• Likely more accuracy coming
13
/ 2 1.001 159 652 180 850.000 000 000 000 76 7.6 10
g−
=
± ×
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Gabrielse
New Determination of the Fine Structure Constant
2
0
14
ec
απε
=• Strength of the electromagnetic interaction• Important component of our system of
fundamental constants
1
10
137.035 999 7100.000 000 096 7.0 10
α −
−
=
± ×
• First improved measurementsince 1987
• Ten times more accurate thanatom-recoil methods
• Component of new mass standard
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Gabrielse
Digressionto Illustrate Quantum Limit
of One Particle in a Trap
is over
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Gabrielse
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Gabrielse
Antihydrogen Offers a More Stringent Probethan Q/M of Antiproton and Proton
CPT Testby comparing
Q/M of antiproton and proton
CPT Testby comparing
laser spectroscopy of antihydrogen and hydrogen
9 x 10-11 much more accurate
Old Long Term Goal New Long Term Goal
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Gabrielse
Motivations and Goals
Clear, Stable, Long Term
• Clear before the AD was built• Clear while the AD rested for 1.5 years• Clear now• Clear in the future
Highly accurate spectroscopic comparisons of antihydrogen atoms and hydrogen atoms
Extremely accurate CPT testsGravitational studies
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Gabrielse
Comparing the CPT TestsWarning – without CPT violation models it is hard to compare
19 x 10-119 x 10-11P Pbaryons
1032 x 10-92 x 10-12e+ e-
Leptons
10152 x 10-32 x 10-18K0 K0
Mesons
FreeGift
MeasurementAccuracy
CPT TestAccuracy
_
_
improve withantihydrogen
3 fu
ndam
enta
lly d
iffer
ent t
ypes
of p
artic
les
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Gabrielse
Seek to Improve Lepton and Baryon CPT Tests
ATRAP members
2 2[ ] [[H] 1 /[ ] [ ] [
[H]]
[ ] [ ] []
] [1[ /] ]qm e q e m ep M pq p Mm e q e m pe
RR
+ + −
∞− +
∞−
+= +
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Gabrielse
Why Cold Antihydrogen?
Goal: Highly Accurate Comparison – Antihydrogen and Hydrogen
No Hope with Hot Antihydrogen • too fast v ~ c• little measurement time• too few atoms
1995 – CERN1997 -- Fermilab
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GabrielseHydrogen 1s – 2s Spectroscopy
(Haensch, et al., Max Planck Soc., Garching)http://www.mpq.mpg.de/~haensch/hydrogen/h.html
Many fewer antihydrogen atoms will likely be available
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Gabrielse
Not as Accurate Yet, but Similar Environment
Still uses a lot more hydrogen atoms than we expect to have antihydrogen atoms
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Gabrielse
Spectroscopy on 1000 or Fewer AtomsSeems Possible 1 part in 1012 estimated
T. Haensch and C. Zimmerman,Laser Spectroscopy of Hydrogen and Antihydrogen,Hyper. Int. 76, 47 (1993).
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Gabrielse
Gravity and Antihydrogen
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Gabrielse
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Gabrielse
Accumulating Many Antiprotons in a Trap
• Slow antiprotons in matter• Capture antiprotons in flight• Electron cooling 4.2 K• 5 x 10-17 Torr
Basic Ideas and TechniquesDeveloped by Our TRAP Collaboration
at CERN’s LEAR: 1986 - 2000)
Used by 3 collaborations at the CERN ADATRAP, ATHENA and ASACUSA
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Gabrielse
We Go to CERN
France
Switzerland (Geneva)
Makes matter and antimatter particles
skiing
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Gabrielse
Harvard UniversityProf. G. Gabrielse Dr. T. Roach J. Estrada A. Speck(Spokesperson) Dr. J.N. Tan P. Yesley D. Lesage
Dr. C. Storry P. Oxley P. LarochelleDr. J. Tan N. BowdenDr. B. Levitt M. Wessels
Juelich LaboratoryDr. W. Oelert Dr. T. Sefzick Z. Zhang
Dr. G. SchepersDr. D. Grzonka
Max Planck Institute for Quantum OpticsProf. T. Haensch Dr. J. Walz H. Pittner
M. Herrmann
York UniversityProf. E. Hessels D. ComeauProf. C. Storry
University of MainzProf. J. Walz
ATRAP
Earlier contributions from Bonn and Vienna
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GabrielseFor a low energy, laboratory physicistgoing to a particle physics lab was an adventure
1981 ventured to Fermilab as a postdoconly one person was interested “Tev or bust”
1986 go to CERN (still essentially a postdoc)get thrown out of first officeget 24 hours of antiproton beam to demonstrate slowingget 24 hours to demonstrate trapping
Amazingly, this worked CERN extended more hospitality(postdoc professor)
Continuing challenge: the way that we must invent our way throughour experiments is very different from the highlyscheduled modern particle experiments
still not well understood by committees, etc.
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Gabrielse
Antiproton Capture – the Movie
z position
Axia
l Ene
rgy
z position
r pos
ition
p
p
pp
"First Capture of Antiprotons in a Penning Trap: A KeV Source",G. Gabrielse, X. Fei, K. Helmerson, S.L. Rolston, R. Tjoelker, T.A. Trainor, H. Kalinowsky, J. Haas, and W. Kells; Phys. Rev. Lett. 57, 2504 (1986).
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Gabrielse
z position
Axia
l Ene
rgy
Electron-Cooling of Antiprotons – in a Trap
p
p
e-
• Antiprotons cool via collisions with electrons • Electrons radiate away excess energy
"Cooling and Slowing of Trapped Antiprotons Below 100 meV",G. Gabrielse, X. Fei, L.A. Orozco, R. Tjoelker, J. Haas, H. Kalinowsky, T.A. Trainor, W. Kells; Phys. Rev. Lett. 63, 1360 (1989).
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Gabrielse
1981 – 1985 Proposals- Fermilab- CERN
1986 Slow antiprotons in matter21 MeV 3 keV
1986 First trapping of antiprotons< 300 < 3 keV ~10 minutes
1989 Hold 105 antiprotons for 2 monthslifetime > 3.4 monthspressure < 5 x 10-17 Torr
1989 First electron cooling in trap3 keV 0.3 meV (4.2 K)
1990 First antiproton stacking in trap
1990 q/m of antiproton and proton same to 4 x 10-8
1992 First observation of one trapped antiproton
1995 q/m of antiproton and proton same to 1 x 10-9
1999 q/m of antiproton and proton same to 9 x 10-11
106-fold improvement overall other techniques
First antiproton trap
Antiproton Years: TRAP at CERN’s LEAR
antiprotons
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Gabrielse
• Phys. Rev. Lett. 57, 2504 (1986).
• Phys. Lett. A 129, 38 (1988)
• Phys. Rev. Lett. 63, 1360 (1989).
• Phys. Rev. A (Rapid Comm.) 40, 481 (1989).
• Phys. Rev. Lett. 65, 1317 (1990).
• Sci. Am., Dec. , pp. 78 – 89 (1992).
• Phys. Rev. Lett. 75, 806 (1995).
• Phys. Rev. Lett. 74, 3544 (1995).
• Phys. Rev. Lett. 77, 806 (1996).
• Phys. Rev. Lett. 82, 3198 (1999).
• Phys. Lett. B 455, 311 (1999).
• Phys. Rev. Lett. (14 Feb. 2000).
Key TRAP Publications
First trapping of antiprotons
4.2 K antiprotons and positronsinteracting (preparing for antihydrogen)
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Gabrielse
LEAR – Low Energy Antiproton Ring (at CERN)
Built to slowly spill antiprotonsmeson spectroscopy and CP studies
we persuaded CERN to give us antiprotonpulses instead
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GabrielseLEAR – Low Energy Antiproton Ring
AC – catch antiprotonsAA – stack antiprotons, coolLEAR – decelerate antiprotons
We got 109 antiprotons in a pulse every 5 minutes(maximum, need refill time)
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Gabrielse
CERN – the Largest and Smallest Accelerators
70 mK, lowest storage energyfor any charged particles
2p2M c
LEAR and AD
TRAP
1010
4.2 K0.3 meV
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Gabrielse
Accumulating Antiprotons – just a matter of time
ATRAP’s good vacuum < 5 x 10-17 Torrallows such stacking
(ATHENA and ASACUSAuse stacking but with lessbunches)
“Stacking”
Can stack this numberin a single well, for moreneed multiple wells
First Demonstration – Antiprotons Stacked in a TrapG. Gabrielse, X. Fei, L.A. Orozco, R. Tjoelker, J. Haas, H. Kalinowsky, T.A. Trainor, W. KellsPhys. Rev. Lett. 63, 1360 (1989)
“Stacking of Cold Antiprotons”ATRAPPhys. Lett. B 548, 140 (2002)
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Gabrielse
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Gabrielse
Making Atoms Entirely of Antimatter
Antihydrogen atoms
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Gabrielse
Cold Antihydrogen Aspirations Announced Long Ago
“For me, the most attractive way ... would be to capture the antihydrogen in a neutral particle trap ... The objective would be to then study the properties of a small number of [antihydrogen] atoms confined in the neutral trap for a long time.”
Gerald Gabrielse, 1986 Erice Lecture (shortly after first pbartrapping) In Fundamental Symmetries, (P.Bloch, P. Paulopoulos, and
R. Klapisch, Eds.) p. 59, Plenum, New York (1987).
Goals• Produce cold antihydrogen• Trap cold antihydrogen• Use accurate laser spectroscopy to compare
antihydrogen and hydrogen
4.2K
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Gabrielse
Meanwhile: Very Fast Antihydrogen Atoms
First at CERN in Geneva, Switzerland"Production of Antihydrogen" G.Baur et al. (team led by W. Oelert) Phys.Lett. B 368 (1996) 251-258.
Then at Fermilab in the USA"Observation of Antihydrogen" G. Blanford, et al. Phys. Rev. Lett. 80, 3037 (1998).
Demonstrated the existence of antihydrogen atoms.
Need slow antihydrogen for precise study
too few atoms
atoms go too fastcannot make accurate comparisonsof antihydrogen and hydrogen
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Gabrielse
1. In a nested Penning trap, during positron cooling of antiprotons
Device and technique – TRAP and ATRAP (1986 – 2001) Used to produce slow antihydrogen – ATHENA and ATRAP
(2002)
2. Laser-controlled resonant charge exchange
Developed the technique – Harvard and York (2001-2003)ATRAP (2004)Only a few atoms made so far – proof-of-principle
Now: Two Ways to Produce Slow Antihydrogen
Two Ways That Do Not (Yet) Produce Slow Antihydrogen1. Field-assisted formation – ATRAP (2002)2. Laser stimulated formation with CO2 laser – ATHENA (2004)
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GabrielseMethod 1: Nested Penning Trap3-Body “Recombination”
Nested Penning Trap 3-Body “Recombination”
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Gabrielse
e+
p
Method 1: Positron Cooling of Antiprotonsin a Nested Penning Trap
TRAP/ATRAP Develops the Nested Penning TrapProposed nested trap as a way to make antihydrogen"Antihydrogen Production Using Trapped Plasmas"G. Gabrielse, L. Haarsma, S. Rolston and W. KellsPhysics Letters A 129, 38 (1988)
"Electron-Cooling of Protons in a Nested Penning Trap"D.S. Hall, G. GabrielsePhys. Rev. Lett. 77, 1962 (1996)
"First Positron Cooling of Antiprotons"ATRAPPhys. Lett. B 507, 1 (2001)
Cold antihydrogen wasmade in 2001 not cleanly detected
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Gabrielse
One Production Method– Two Detection Techniques
2001: ATRAP, "First Positron Cooling of Antiprotons"Phys. Lett. B 507, 1 (2001)
Crucial Device: Nested Penning TrapCrucial Technique: Positron Cooling of Antiprotons
Cold trapped positrons cool antiprotons to a low relativevelocity with the positrons produces slow antihydrogen
2002: ATHENA and ATRAP demonstrated that antihydrogenwas produced by this device and techniqueATHENA, Nature 419, 456 (2002)
ATRAP, Phys. Rev. Lett. 89, 213401 (2002)ATRAP, Phys. Rev. Lett. 89, 233401 (2002)
same productiondifferent detection
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Gabrielse
Comparing the Two Detection MethodsAthena – detects positron and antiproton annihilations within
5 microseconds and +/- 8 mm of each other(now using mostly antiproton annihilations, 4 mm resolution)
Good: Detects antihydrogen whatever is velocity and stateNot as good: Insensitive to antihydrogen velocity and state
ATRAP – field ionization detection
Good: No backgroundProbes internal state of the antihydrogenCan measure antihydrogen velocity
Not as good: Can only detect states that can be field ionized(Hope to use lasers to excite lower states to statesthat can be field ionized)
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GabrielseATRAP’s Field Ionization Method
• Use Field-Ionization – strip positron and store antiproton
p
e+H
p
e+
• Dump stripping well after experiment– Dump other particles before looking in stripping well– Ramp quickly compared to cosmic background count rate (ramp
in 20ms, get one cosmic/second)– Essentially no background for this measurement!
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GabrielseOnly Detect Ionized Antihydrogen
• Field-Ionization is very robust – only antihydrogen can get antiprotons into the stripping well
p
e+
p
• Antiprotons knocked out of well leave to the left
• Even if an antiproton has enough energy to get to the ionization well, it can not get into the well
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Gabrielse
pe+
Driven Antihydrogen Production Higher Rate• Recall that antiprotons cool below the positrons –
interaction stops• Drive axial motion of antiprotons repeatedly to “drive”
interaction
• Antihydrogen production rate is increased by more than an order of magnitude using this method
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Gabrielse
No Useful Antihydrogen Yet,But We Have Methods to Measure and Optimize
ATRAP’s field ionization method is only probe so farHow close to the ground state?
How cold?Vary ionization field F in time to find out.
• Fast atoms make it through while field is at a low value.• Slow atoms never avoid ionization
F ~ Cos(ωt)
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Gabrielse
Observed Antihydrogen Atoms are Very Weakly Bound
Breakdown of the GCA picture chaotic motion?
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GabrielseSimulation of Field Ionization Spectrum
GCA, beforecharge exchange
GCA, after charge exchange
GCA
ATRAP Measurement
Full simulation
T. Pohl, H. R. Sadeghpour and G. GabrielseTalk here: Pohl
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Gabrielse
First Measurement of an Antihydrogen Velocity
200 meV
• This is for the most weakly bound antihydrogen states• More deeply bound states may be going more slowly
20thermal
vv
∼
ATRAP, "First Measurement of the Velocity of Slow Antihydrogen Atoms", Phys. Rev. Lett. 93, 073401 (2004).
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Gabrielse
More Favorable InterpretationCharge exchange of antihydrogen with faster protons
T. Pohl, H. R. Sadeghpour and G. GabrielseTalk here: Pohl
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Gabrielse
Great Features of Method I
• High antihydrogen production rate• Easy and robust
Not-so-Great (so Far)
• Highly excited antihydrogen is produced• Detected antihydrogen has velocity much higher
average for 4.2 K• Variations from production attempt to production attempt is
larger than we understand (something not under control)
Conclusion: Need larger trap and more positronsMore collisional deexcitationMore collisional coolingMore stability in the production process (away from trap walls)
(big mystery!)
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Gabrielse
Observe Rydberg Cs and Rydberg Positronium (at Harvard)
Observe Antihydrogen n~37 (at CERN)State-selected antihydrogen, should be very coldhope to de-excite with a laser (not easy) or collisions
First Laser-Controlled Antihydrogen ProductionUse positronium – Deutch, …Use Rydberg positronium – Charlton, …Use charge exchange to produce the positronium – Hessels, …
Calculation (no B field): E.A. Hessels, D.M. Homan, M.J. Cavagnero, Phys. Rev. A 57, 1668 (1998).
Very Different Method II to Produce Slow Antihydrogen
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Gabrielse
Antihydrogen Via Laser-Controlled Resonant Charge Exchange
852 nm
510.6 nm
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Gabrielse
Great Features of Method II
• Lasers control the state of the antihydrogen produced• Likely the first truly cold antihydrogen
Not-so-Great (so Far)
• Highly excited antihydrogen is produced• Detection rate is very low (production rate is much better)
Conclusion: Need larger trap and more positronsMore detectable antihydrogen to work with
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Gabrielse
Current “Do or Die” Challenges(no change since Villars)
1. Deexcite the highly excited antihydrogen that is produced.2. Need slower antihydrogen produced (in method I)3. Add field gradients of a magnet trap for antihydrogen
without destroying the antihydrogen production rate
Larger traps with more positrons and antiprotonsRoom for magnetic gradient trapsRoom for laser access
We believe that a solution requires
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Gabrielse
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Gabrielse
ATRAP II – Completely New
Much Bigger room for bigger trap, more particles, more coolingroom for magnetic traproom for more laser accessroom for annihilation imaging
New Beam Steering, New Soleniod, New Dewars, New Detectors, New Electronics, New Positron Source, …
What to do when CERN shuts us down for a year and one half, and delivers less antiproton beam during the first year back?
Build a completely new apparatus based upon what we have learned at the AD
Will we be ready? We still hope so, but this will be a verybusy beam run.
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Gabrielse
Harvard UniversityProf. G. Gabrielse Dr. B. Levitt D. Le Sage(Spokesperson) Dr. I. Kuljanishvili P. Larochelle
Dr. J. Wrubel W. Kolthamme
Juelich LaboratoryDr. W. Oelert Dr. D. Grzonka Z. Zhang
Dr. F. GoldenbaumDr. T. Sefzick
York UniversityProf. E. Hessels M. George D. ComeauProf. C. Storry M. Weel A. Carew
University of MainzProf.. J. Walz F. Markert
Rowland Institute at HarvardDr. A. Speck
Free Univesity of AmsterdamProf. E. Eikema
Max Planck Institute for Quantum OpticsProf. T. Haensch
ATRAP 2006
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GabrielseComparing ATRAP I to ATRAP II
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Gabrielse
Some ATRAP Members at a Recent MeetingHarvard, 13 January 2006
Missing: Some ATRAP members from Juelich, Rowland, Mainz, Amsterdam
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Gabrielse
Different Configurations Envisioned for ATRAP II
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Gabrielse
Connection to the AD
AD antiprotons
ATRAP IISolenoid
AD Team is correcting for the fringing field
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Gabrielse
Location of Positron Source for ATRAP II
ATRAP IISolenoidand Traps
positron source(locally shielded)
low energylow flux
positron guide
ATRAP I
could be a fence, if this is more convenient than concrete
rear entrance A new sodiumsource shouldarrive soon.
Will it???
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Gabrielse
Coming
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Gabrielse
A Trap for Antimatter Atoms
Atom with a properly alligned magnetic momentwill be trapped in a minimum of magnetic field
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Gabrielse
Conclusions
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Gabrielse
Where We Are, and Where We are Going
A lot has been accomplished• We can regularly cool antimatter particles to extremely
low energies• We can readily make many antihydrogen atoms
Much remains to be done• Need to make antihydrogen atoms in their ground state• Need to slow the antihydrogen atoms even more to trap them(some may be cold enough)
Goal• Use lasers to probe for any tiny differences between
atoms of antimatter and matter
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Gabrielse
Why Study Antimatter?Solve energy shortage problem, make weapons, make rockets
Look closely for any tiny differences between antimatter and matter• Test basic theories that suggest that matter and antimatter
are opposite in charge, but identical in mass, …• Probing reality at its most fundamental level
Such fundamental experiments typically lead to new technologiese.g. Transistor, Laser, World Wide Web (CERN)e.g. From our experiments so far
• new cell designs for ion cyclotron resonance imaging of pharmaceuticals
• self-shielding solenoid used for NMR and MRI imaging• first continuous Lyman alpha radiation
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Gabrielse
If Antimatter Atoms Interest You
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Gabrielse
Antihydrogen Review Paper"Atoms Made Entirely of Antimatter: Two Methods Produce Slow Antihydrogen"G. GabrielseAdvances in Atomic, Molecular and Optical Physics 50 (2004).
Simpler Discussions“Extremely Cold Antiprotons"G. GabrielseScientific American 50 (1986)
“Making Cold Antimatter”G.P. CollinsScientific American (June, 2005)